Citric acid is a common material of natural origin. The structure is:
CAS Registry Number: 77-92-9CA Index Name: 1,2,3-Propanetricarboxylic acid, 2-hydroxy-
Citric acid is made by fermentation, using cultures of Aspergillus niger are fed on a sucrose or glucose-containing medium.
Citric acid is one of a series of compounds involved in the physiological oxidation of fats, proteins, and carbohydrates to carbon dioxide and water. This series of chemical reactions is central to nearly all metabolic reactions, and is the source of two-thirds of the food-derived energy in higher organisms. Krebs received the 1953 Nobel Prize in Physiology or Medicine for the discovery. The series of reactions is known by various names, including the citric acid cycle, the Krebs cycle, and the tricarboxylic acid cycle
Citrate esters are known. They conform to the following structure:
The esters are made by the reaction of fatty alcohols with citric acid.
U.S. Pat. No. 4,292,192 issued to Hooper, et al. teaches that Detergent bars for personal washing are given a deodorant property by including an ester of citric acid. The ester may be an acetyl derivative. The amount of ester used will be in the range of from about 0.3% to about 3%. Examples of the esters are triethyl citrate and acetyl tributyl citrate.
U.S. Pat. No. 2,122,716 describes long chain esters of citric acid, e.g., tridodecyl citrate, which have been used as plasticizers for resinous compositions.
U.S. Pat. Nos. 3,239,555 and 3,241,992 disclose bis-citric acid esters made by esterifying the acid groups with C1 to C18 alcohols and coupling the esters with dibasic acids. Such esters are useful as plasticizers for plastics.
U.S. Pat. No. 3,251,792, the acid groups of citric acid are esterified with alkyl, aryl, cycloalkyl and haloaryl alcohols and the hydroxyl group is esterified with a carbonyl compound. Such compounds are used as stabilizers for polypropylene.
U.S. Pat. No. 5,089,658 issued Feb. 18, 1992 to Elmore et al, is directed to citric acid esters. In one aspect, this invention pertains to citric acid esters which contain at least one primary or secondary hydroxyl group. In another aspect, this invention relates to citric acid esters which are reactive diluents. In still another aspect, this invention pertains to citric esters which are pigment dispersants.
The citric ester compositions of this invention are useful as reactive diluents for high solids thermosetting coating composition and as pigment dispersants for use in thermosetting coatings.
U.S. Pat. No. 4,868,236 to O'Lenick discloses a guerbet citric ester and polymers thereof useful in plastic lubrication.
None of these patents provide polyester derivatives of mixed fatty esters of citrate as envisioned by the present invention.